Ultrasonic wave delay device having a trap zone for undesired signal components

ABSTRACT

An ultrasonic wave delay device for delaying an ultrasonic wave signal a predetermined time by propagating the ultrasonic wave signal through a solid propagation medium, in which principal signal component reflection surfaces constituting a path of propagation for principal components of the signal are arranged in the solid component propagation zone in the solid propagation medium and cause unnecessary components of the signal to escape from the principal signal component propagation zone. Reflection surfaces exclusively for the unnecessary signal components may be provided adjacent the principal signal component propagation zone in the solid propagation medium, whereby the unnecessary signal components can be subjected to multiple reflection between the unnecessary signal component reflection surfaces and outer walls of the solid propagation medium to ensure that the unnecessary signal components become extinct.

United States Patent Yamamoto 1 1 July 25, 1972 [54] ULTRASONIC WAVEDELAY DEVICE 3,400,341 9/1968 Sittig ..333/30 R HAVING A TRAP ZONE FORUNDESIRED SIGNAL COWONENTS FOREIGN PATENTS 0R APPLICATIONS 4 705,0803/l954 Great Britain ..333/30 R [72] Inventor: Toshiaki Yamamoto, Tokyo,Japan Primary Examiner-Eli Lieberman [73] Asslgnee ztgg g f gggg ofJapan Limited Assistant Examiner-Marvin Nussbaum Attorney-Stevens,Davis, Miller 8L Mosher [22] Filed: Dec. 4, 1970 211 App]. No.: 95,018[57] ABSTRACT An ultrasonic wave delay device for delaying an ultrasonicwave signal a predetermined time by propagating the ul- [30] Fm'gnApphcation mom), Data trasonic wave signal through a solid propagationmedium, in

Dec. 6, 1969 Japan ..44/98087 which principal signal componentreflection surfaces constituting a path of propagation for principalcomponents of the 52 us. 01. ..333/30 R, 333/72 Signal are arranged inthe Solid component P p g zone 51 1 1111. C1 ..H03h 7/30, 110311 9/30 inthe solid Propagation medium and eeuse unnecessary [58] Field of Search..333/30, 71, 72; 310/8, 8. 1, ponents of the signal to eeeepe m thePrincipal Signal 3310/96, 9.7 ponent propagation zone. Reflectionsurfaces exclusively for the unnecessary signal components may beprovided adjacent 56] References cited the principal signal componentpropagation zone in the solid propagation medium, whereby theunnecessary signal com- UNITED STATES NTS ponents can be subjected tomultiple reflection between the unnecessary signal component reflectionsurfaces and outer 2,907,958 10/1959 Skaggs "333/30 R walls of the solidpropagation medium to ensure that the un- 2, 1960 Y- necessar si nalcorn onents become extinct. 2,263,902 11/1941 Percival ..333/30 R y g p3,593,213 7/1971 Franx et al. ..333/30 R 3 Claims, 6 Drawing figuresPAIENTEDJuL2S I972 3.680.008

sum 1 or 2 ZWmqmara IN VENTOR BY Z M ATTORNEY! ULTRASONIC WAVE DELAYDEVICE HAVING A TRAP ZONE FOR UNDESIRED SIGNAL COMPONENTS This inventionrelates to ultrasonic wave delay devices, and more particularly it isconcerned with an ultrasonic wave delay device which permits effectiveremoval by a simple structure of the unnecessary components from anultrasonic wave signal propagated through a solid propagation medium.

It has been the usual practice in the electric communicationequipmentindustry to cause an electric signal to be delayed a predetermined timeby propagating the signal through a solid propagation medium afterconverting the electric signal into an acoustic signal by means of anelectro-acoustic transducer and reconverting the signal back into anelectric signal by means of an acousto-electric transducer element whenit emerges from the solid propagation medium.

Generally, it is essential that any circuit element built into anelectric circuit be compact in size. This is also true of an ultrasonicwave delay device intended for use in attaining the aforementionedobject. Therefore, it has hitherto been customary to produce a compactultrasonic wave delay device wherein a number of reflection surfaces areprovided in a medium for propagating an ultrasonic wave signal so as todefine an ultrasonic wave propagation path therein in accordance with aso-called multiple reflection process.

When the multiple reflection process is employed for producing a compactultrasonic wave delay device, the electro-acoustic transducer elementprovided in an input end of the device and the acousto-electrictransducer element provided in an output end thereof must be compact insize. Reduction in size of the electro-acoustic transducer elementresults in a reduction in the area of its oscillation surface, and theradiation characteristics of the oscillation surface of a smallelectro-acoustic transducer element have a directivity such that asupersonic wave signal is not only directed to a predetermined path ofpropagation for the ultrasonic wave signal (principal ultrasonic wavesignal component propagation path) but also transmitted in otherdirections as well. Thus, an ultrasonic wave signal produced by thecompact electro-acoustic transducer element moves in other directionsthan the direction in which it is intended to move through the principalultrasonic wave signal component propagation path, so that somecomponents of the ultrasonic wave signal (which are unnecessarycomponents of the signal) are transmitted through other paths in thepropagation medium than the principal ultrasonic wave signal componentpath to the acoustoelectric transducer element at the output end of thepropagation medium.

The unnecessary signal components differ from the principal signalcomponents in the time in which they are delayed in being transmittedthrough the propagation medium. Thus, it is essential in ultrasonic wavedelay devices of the type described that the unnecessary signalcomponents should be eliminated. Many proposals have hitherto been madefor solving this problem.

Known devices. for obviating the problem of how to eliminate theunnecessary signal components from an acoustic signal have all beenunsatisfactory in attaining the end for which they are intended. Nosatisfactory ultrasonic wave delay device has ever been developed whichis simple in' construction and yet effective in removing the unnecessarysignal components from an ultrasonic wave.

This invention is intended to provide a novel ultrasonic wave delaydevice which obviates the aforementioned disadvantages of devices of theprior art.

Accordingly, a principal object of the present invention is to providean ultrasonic wave delay device which is compact in size, simple inconstruction, and yet effective to remove unnecessary components from anultrasonic wave signal.

Another object of the invention is to provide an ultrasonic wave delaydevice in which a solid propagation medium is used for transmitting anultrasonic wave signal therethrough, and which lends itself tofabrication with ease by means of an ultrasonic processing operation orby using a press.

A further object of the invention is to provide an ultrasonic wave delaydevice in which reflection surfaces for principal components of anultrasonic wave signal are provided in the interior of an ultrasonicwave signal propagation medium for forming a path of propagation for theprincipal components of the signal in the propagation medium.

Still another object of the invention is to provide an ultrasonic wavedelay device effective to remove unnecessary components from anultrasonic wave signal by employing a multiple reflection process in thefabrication of an ultrasonic wave propagation medium, in which there areprovided reflection surfaces for principal components of the signal andreflection surfaces for the unnecessary components thereof in theinterior of the propagation medium, such two types of surfaces beingarranged in a specific manner for effectively eliminating theunnecessary signal components. I

A still further object of the invention is to provide an ultrasonic wavedelay device in which reflective surfaces for principal components of anultrasonic wave signal are provided in the interior of an ultrasonicwave propagation medium so as to thereby define a principal signalcomponent propagation zone therein, and in which unnecessary componentsof the signal are effectively removed in portions of the propagationmedium other than the principal signal component propagation zone.

Yet a further object of the invention is to provide an ultrasonic wavedelay device in which at least one of a plurality of reflection surfacesfor principal components of an ultrasonic wave signal provided in thepath of propagation for the principal components of the signal isconstructed such that its configuration and area are substantially equalto the crosssectional configuration and area of the principal componentsof the signal incident thereon, whereby unnecessary components of thesignal can be removed with increased effectiveness.

Additional objects as well as features and advantages of this inventionwill become evident from the description set forth hereinafter whenconsidered in conjunction with the accompanying drawings, in which:

FIG. I is a view in explanation of the ultrasonic wave delay deviceincorporating one embodiment of this invention;

FIG. 2 is a perspective view of a modification of theembodimentillustrated in FIG. 1;

FIG. 3 is a view in explanation of the ultrasonic wave delay devicecomprising a second embodiment of this invention;

FIG. 4 is a view in explanation of the ultrasonic device comprising athird embodiment of this invention;

FIG. 5 is a perspective view of a modification of the third embodimentof the invention; and

FIG. 6 is a view in explanation of one example of means for attaching atransducer element to a propagation medium in the device according tothis invention.

In FIGS. 1 to 5, an electro-acoustic transducer element I l is attachedto one portion of an outer wall of a rectangular propagation medium 10for an ultrasonic wave which is made,

for example, of iron, aluminum, glass, ceramics or the like,

and an acousto-electric transducer element 12 is attached to the otherportion of the outer wall of the propagation medium 10.

FIG. 6 shows one example of means for adhering such transducer elementsto the propagation medium. As shown, silver or other metal 13 isdeposited by vaporization in vacuum on a surface of such propagationmedium 10 in a case that the propagation medium 10 is made of glass.Soldered at 17 to the metal layer 13 is the transducer element whichconsists of a transducer 14 sandwiched by electrodes 15 and 16 made ofsilver or the like and attached to opposite surfaces of the transducer14, said transducer element being made of lead titanate-zirconateceramics or crystal and the like.

Input terminals 18 for an input electric signal are connected to theelectrodes 15 and 16 of the electro-acoustic transducer element 11. andoutput terminals 19 for an output electric signal, which has beendelayed a predetermined time, are conducer element 12 so as to form apath of propagation 20 for principal components of an ultrasonic wavesignal therein. Such reflection surfaces are provided by forming aplurality of openings 22, 22, in the interior of the solid medium 10 byultrasonic processing, pressing, or milling.

FIG. 2 shows a modification of the first embodiment of the invention.FIG. 3 shows a second embodiment and FIGS. 4

and 5 show a third embodiment thereof. In these figures, the pluralityof reflection surfaces 21, 21, for forming the path of propagation 20for the principal components of the ultrasonic wave signal in the'solidmedium are provided by I forming aplurality of grooves 23,23, in thesolid medium by cutting inwardly from outer wallsof the solid medium 10by the same means of processing as used in the first embodiment.

The reflection surfaces 21 have a surface grain size ranging from l0 to100 p. which may vary depending on the frequency band of a particularultrasonic wave used. In FIGS. 1 to 5, an inputelectric signalsuppliedto the input terminal 18 is converted into an ultrasonic wave signal byvthe electro-acoustic transducer element 1 l and radiated into the solidmedium 10. As aforementioned, principal components of the ultrasonicwave signal radiated into the solid medium 10 are subjected to multiplereflection between the reflection surfaces 21, 21, for the principalcomponents of the signal provided in the interior of the solid medium10, so that they pass through the predetermined path of travel 20 forthe principal components of the signal and reach the acousto-electrictransducer element 12, where the ultrasonic wave signal is convertedinto an A electric signal again to provide an output electric signalwhich {has been delayed a predetermined time.

On the other hand, unnecessary components of the signal radiated fromthe electro-acoustictransducer element 1 1 into 7 the solid medium l0.are transmitted through a path of propagation 24 for unnecessarycomponents of the signal shown in broken lines in the figures, andultimately reach portions of the solid medium whichare outside a 'zone(principal signal component propagation zone) defined by the reflectionsurfaces 21, 21, for the principal components of the signal,

sothat acoustic energy is converted into thermal energy in' suchportions of the solid medium 10. Thus, the unnecessary components of thesignal are effectively eliminated.

in FIG. 1, there are illustrated sound absorbing members 25 in phantomlines. Such sound absorbing members 25 are illustrated to show that theunnecessary components of the signal deflected from the path ofpropagation 20 for the principal .signal components and not incident onone of the reflecting surfaces 21 for the principal signal componentscan be absorbed'by the sound absorbing members 25 when they reach aportion between the principal signal component propagation zone and anouter wall of the solid medium after they have passed through such zone.The modification of the first embodiment shown in FIG. 2, the second andthird embodiments shown in FIGS. 3 and 4,

and the modification of the third embodiment shown in FIG. 5

are shown as not being provided with the sound absorbing members 25. Itshould be understood, however, that suitable sound absorbing members maybe provided in outer walls of the solid medium 10 in these embodimentsas well, and that the principal signal components are not damped even ifthe sound absorbing membersare' 'attached to the outer walls of thesolid medium along. substantially the entire circumferential extentthereof, because the reflection surfaces for the principal signalcomponents in the instant ultrasonic wave delay device are scatteredindependently of one another in the interior of the solid mediuml0 orprovided by cutting into its interior from its outer walls.-

Any material which is compatible with mechanical impedance of the solidmedium and which hm good adhering and shaping properties, such as anepoxy resin containing powdered metal, for example, may be used formaking such sound absorbing members. I

Referring to FIG. 1 again, lines 20a and 20b represent boundaries of thepath of propagation 20 for the principal signal components. Stateddifferently, they indicate a range of the principal components of theultrasonic wave signal radiated from the electro-acoustic transducerelement 11 into the solid medium 10. Such range corresponds to the widthof a beam of the principal signal components and is from 5 to 10 mm inthis embodiment, although its values may vary depending on the size oftransducer elements used. The lines 20a and 20b may be considered torepresent sides of a cylindrical body having its axis at 20 whosetransverse sectional configuration (transverse sectional configurationof the beam of principal signal components) may vary depending on theshape and configura tion of an oscillation surface of theelectro-acoustic trans ducer element. v s

It will be seen that the present invention resides in the provision ofone or a plurality of reflection surfacesZl, 21, for

the principal signal components in the interiorof the solid medium 10 soas to thereby provide a principal signal com- 7 ponent propagation zonein the interior of the solid medium 7 10. It is one of the features ofthis invention that if, in providing such principal signal componentpropagation zone in the solid medium, the configuration and area of atleast one of the reflection surfaces 21, 21, forming the path ofpropagation 20 for the principal signal components betweenthe'electroacoustic transducer element' 11 and acousto-electrictransducer element 12 aremade substantially equal to the crosssectionalconfiguration and area of the beam of principal signal componentsincident thereon, it is possible to achieve better results in removingthe unnecessary signal components.

When this feature is incorporated in the ultrasonic wave delay device,the configuration and area of the reflection sur-,

face 21 which is disposed in face to face relation with theelectro-acoustic transducer element 11 are preferably made to besubstantially equal to 'the cross-sectional configuration and surfaces21, 21 may be incorporated in the' embodiments shown in FIGS. 3 to 5 aswell.

It will be appreciated that it is possible to effectively eliminate theunnecessary signal components in the present invention by providing theprincipal signal component propagation zone in the interior of the solidmedium 10 which is I defined by thereflection surfaces 21, 21, for theprincipal signal components, soas to cause the unnecessary signalcomponents to be expelled from the principal signal componentpropagation zone. i I i The unnecessary signal components which havebeen expelled from the principal signal component propagation zone inthe interior of the solid medium 10 are subjected to multiple reflectionbetween a plurality of reflection surfaces 26, 26, for the unnecessarysignal components provided in the solid medium 10 but outside theprincipal signal component I propagation zone and outer walls ofthe'solidmedium 10. Thus, the unnecessary signal components are 1gradually deprived of their energy and finally cease to exist;

The reflection surfaces 26, 26, forthe unnecessary signal components areformed by the openings 22, ,22, ."in the first embodiment shown inFlG.I'and'its modification shown in FIG. 2, and by the grooves 23, 23, inthe second and third embodiments shown in FIGS. 3-and 4 respectively andthe modification of the third embodiment shown in FIG.

5. It should be noted that in all the embodiments and theirmodifications the reflection surfaces 26, 26, for the unnecessary signalcomponents are provided in the solid medium but outside the path ofpropagation for the principal signal components.

The reflection surfaces 26, 26, for the unnecessary signal componentsare of such size, shape and construction and disposed in positions suchthat the unnecessary signal components reflected by reflection surfaces27 in the outer walls of the solid medium shown in FIGS. 3 and 4 arereflected by the particular reflection surfaces 26 facing suchreflection surfaces 27 to move in a direction in which the unnecessarysignal components are deflected from the principal signal componentpropagation zone and subjected to multiple reflection between thereflection surfaces 27 in the outer walls of the solid medium and thereflection surfaces 26.

The aforementioned action of the reflection surfaces 26 for theunnecessary signal components is illustrated in FIGS. 3 and 4.

By providing such reflection surfaces 26 for the unnecessary signalcomponents in the solid medium, there is provided, adjacent theaforementioned principal signal propagation zone, an unnecessary signalcomponent trap zone which captures unnecessary signal componentsexpelled from the principal signal component propagation zone to ensurethat they never return to the principal signal component propagationzone. The provision of such unnecessary signal component trap zone inthe solid medium adjacent the principal signal component propagationzone is conducive to increased efficiency in eliminating the unnecessarysignal components.

The dimensions (external dimensions) of the modification of the firstembodiment shown in FIG. 2 are 46 millimeters in transverse width, 40millimeters in longitudinal width and three millimeters in thickness.The dimensions (external dimensions) of the modification of the thirdembodiment shown in FIG. 5 are 40 millimeters in transverse width, 45millimeters in longitudinal width and six millimeters in thickness. Theopenings 22 and grooves 23 in all the embodiments are about 10millimeters in length.

While particular embodiments and modifications thereof of this inventionare shown and described, it will be understood, of course, that theinvention is not to be limited thereto, since many other modificationsand changes may be made and it is contemplated, therefore, by theappended claims, to cover any such modifications as fall within the truespirit and scope of this invention.

What is claimed is:

I. An ultrasonic wave delay device comprising a solid medium forpropagating an ultrasonic wave signal; an electroacoustic transducerelement attached to an outer wall of said solid medium for converting aninput electric signal into an ultrasonic wave signal; a plurality ofreflection surfaces for principal components of the ultrasonic wave forforming a path of propagation for the principal components of theultrasonic wave signal radiated from said electro-acoustic transducerelement into the interior of said solid medium, at least one of saidreflection surfaces for the principal components being provided in theinterior of said solid medium; an acousto-electric transducer elementattached to an outer wall of said solid medium for converting into anoutput electric signal only the principal components transmitted throughthe path of propagation; and at least one reflection surface provided inthe interior of said solid medium for unnecessary components of theultrasonic wave signal transmitted in said solid medium through pathsother than the path of propagation for the principal components, saidreflection surface for the unnecessary components being provided in aportion of said solid medium other than the path of propagation for theprincipal components and forming an unnecessary signal component trapzone between the reflection surface for unnecessary components and anouter wall of said solid medium.

2. An ultrasonic wave delay device as defined in claim I wherein said atleast one of the reflection surfaces for said principal components ofsaid ultrasonlc wave signal and said at least one reflection for saidunnecessary components of said ultrasonic wave signal are provided insaid solid medium by forming an opening or openings therein.

3. An ultrasonic wave delay device as defined in claim I wherein said atleast one of the reflection surfaces for said principal components ofsaid ultrasonic wave signal and said at least one reflection surface forthe unnecessary components of said ultrasonic wave signal are providedin said solid medium by forming a groove or grooves in the solid mediumby cutting inwardly from outer walls thereof.

1. An ultrasonic wave delay device comprising a solid medium forpropagating an ultrasonic wave signal; an electro-acoustic transducerelement attached to an outer wall of said solid medium for converting aninput electric signal into an ultrasonic wave signal; a plurality ofreflection surfaces for principal components of the ultrasonic wave forforming a path of propagation for the principal components of theultrasonic wave signal radiated from said electro-acoustic transducerelement into the interior of said solid medium, at least one of saidreflection surfaces for the principal components being provided in theinterior of said solid medium; an acousto-electric transducer elementattached to an outer wall of said solid medium for converting into anoutput electric signal only the principal components transmitted throughthe path of propagation; and at least one reflection surface provided inthe interior of said solid medium for unnecessary components of theultrasonic wave signal transmitted in said solid medium through pathsother than the path of propagation for the principal components, saidreflection surface for the unnecessary components being provided in aportion of said solid medium other than the path of propagation for theprincipal components and forming an unnecessary signal component trapzone between the reflection surface for unnecessary components and anouter wall of said solid medium.
 2. An ultrasonic wave delay device asdefined in claim 1 wherein said at least one of the reflection surfacesfor said principal components of said ultrasonic wave signal and said atleast one reflection for said unnecessary components of said ultrasonicwave signal are provided in said solid medium by forming an opening oropenings therein.
 3. An ultrasonic wave delay device as defined in claim1 wherein said at least one of the reflection surfaces for saidprincipal components of said ultrasonic wave signal and said at leastone reflection surface for the unnecessary components of said ultrasonicwave signal are provided in said solid medium by forming a groove orgrooves in the solid medium by cutting inwardly from outer wallsthereof.